Abscission is the ability of plants to slough off organs, such as fruit, by an active separation of cells. Abscission results from the formation of a starch-filled abscission layer of cells in the area of the fruit rind, which separates the stem from the fruit. Abscission occurs as cells in the abscission layer begin to separate, eventually dropping the fruit from the stem.
Commercial harvesting of fruit can require deviation from the natural abscission cycle. When harvesting takes place where the abscission layer has not begun to separate, a great deal of force can be required to remove the fruit. The force can damage the fruit or the plant. Presently available abscission agents, such as ethephon, can cause unwanted defoliation, gummosis, immature fruit drop, and rind damage. Abscission agents are needed that do not cause these undesirable side effects.
It is an object of the invention to provide methods and compositions for inducing fruit abscission in plants and trees. This and other objects of the invention are provided by one or more of the embodiments described below.
One embodiment of the invention provides a composition for inducing abscission comprising coronatine and one or more surfactants. The surfactant can be, for example, Tween(copyright)-20 ((sorbitan mono-9 octadecenoate poly(oxy-1,1-ethanedlyl)) or Kinetic(copyright) proprietary blend of poloyalkylene oxide modified polydimethyl siloxane and non-ionic surfactant. The volume by volume of the surfactant can be about 1.0% to about 0.01%. Preferably, the concentration of coronatine is about 10 mg/L to about 1,000 mg/L. More preferably, the concentration of coronatine is about 50 mg/L to about 500 mg/L. Even more preferably, the concentration of coronatine is about 100 mg/L to about 300 mg/L.
Another embodiment of the invention provides a method of inducing fruit abscission comprising administering an effective amount of coronatine to a fruit-bearing plant or tree. The fruit-bearing plant or tree can be, for example, citrus, such as orange, apple, or cherry.
Even another embodiment of the invention provides a method of harvesting fruit from a plant or tree. The method comprises administering an effective amount of coronatine to a fruit-bearing plant or tree and exerting sufficient force on the fruit to separate the fruit from the plant or tree. The harvesting can be accomplished by manual or mechanical methods.
Thus, the invention provides methods and compositions for inducing fruit abscission without excessive defoliation or gummosis, immature fruit drop, or rind damage.